This information is from p. 3 of Barge Canal / Mohawk River Flooding at Schenectady Examined: A Report to the People of Schenectady by James E. Duggan (Schenectady, 2007), and is reproduced here with permission of the author.

The Mohawk River was relatively shallow under normal conditions, flowing actively through its historically important valley as the settlers poled their bateaux upriver and returned more easily. It drains 3,450 square miles, and 185 billion gallons reportedly pass Schenectady annually. The 19th-century Erie Canal was a "land canal" separate from the river, which remained relatively unmodified until New York State acted assertively to enable much-larger vessels of the 20th century to compete against the railroads in crossing the state more easily.

New York State hugely transformed the eastward-flowing portion of the Mohawk River to serve directly in its Barge Canal System. New dams for locks created flat pools, aided by channeling of the riverbed between Rome and Waterford, twenty miles east from Schenectady and almost two-hundred feet lower at the Hudson River's flow to New York City.

Dams creating the pools west and east of Schenectady are vastly different. Westward, a variety of bridging structures span piers in the riverbed to allow dropping the dams section-by-section during the spring and lifting them during November — for the winter and early spring, the channelized portion of the riverbed normally contains most of the swift flow. Crossing between Niskayuna and Clifton Park, the Vischers Ferry Dam is a permanent structure with no flow-managing parts. It involves a "lift" of 27 feet for vessels to move between the (lower) Cohoes and (upper) Niskayuna-Schenectady pools. These two pools serve to "flatten" the prior distinctly sloping flow of the river from Rexford to the final Cohoes Falls and rapids below.

Navigation-season "flash-boards", begun in 1922, raise the level of the Niskayuna-Schenectady Pool at least two feet above the crest of the dam. The reason — at the Clifton Park end of this dam, nearly 2,000 feet long, and as a later section will detail, the New York Power Authority turbines exploit the pool-to-pool fall of the flow. The extra height assures high output of power.

Floods at Schenectady vary in nature, timing and duration. Historically and to this day, ice-jams among the islands and at bends dominate (80%) as the apparent cause. Distinguishing between their site and cause will receive significant attention, as will the matter of open-water or free-flow discharges from the overall drainage basin. Surprisingly major open-water or free-flow floods do occur at Schenectady (e.g., mid-October 1955, perhaps similar to Hurricane "Agnes" in its destructive travel along the Susquehanna drainage basin during the early 1970's).

A person easily could underestimate how much the Pool's width varies in its winding flow-path — from approximately 500 feet at Schenectady to at least 1,500 feet at the Vischers Ferry Dam. The large contrast of the latter width and its suspected physical consequence with respect to flooding will arise in at least two later sections herein.

At Union College, several studies (as funded partially by the National Science Foundation) have produced some significant information regarding the Niskayuna-Schenectady Pool's major ice-jam locations affecting Schenectady, the applicable history of weather, hydrology and flooding, as well as related topics — but not any significant examination of the Vischers Ferry Dam / Lock 7 complex as having a substantial role.

This examination about flooding at Schenectady focuses on that early-20th century dam, flash-boards and the year-round Niskayuna-Schenectady Pool impounded for navigation and power.